go-delve/delve · error

expected argument after -size

Error message

expected argument after -size

What it means

The `-size` flag of the examineMemory command requires a following argument. ParseExamineMemoryArg calls nextArg(); if the flag is the last token on the line (or followed only by whitespace) there is nothing to parse and Delve returns this error immediately.

Source

Thrown at service/api/command.go:249

				out.Format, ok = fmtMapToPriFmt[arg]
				if !ok {
					return nil, fmt.Errorf("%q is not a valid format", arg)
				}
			}
		case "-count", "-len":
			arg := nextArg()
			if arg == "" {
				return nil, errors.New("expected argument after -count/-len")
			}
			var err error
			out.Count, err = strconv.ParseInt(arg, 0, 64)
			if err != nil || out.Count <= 0 {
				return nil, errors.New("count/len must be a positive integer")
			}
		case "-size":
			arg := nextArg()
			if arg == "" {
				return nil, errors.New("expected argument after -size")
			}
			var err error
			out.Size, err = strconv.ParseInt(arg, 0, 64)
			if err != nil || out.Size <= 0 || out.Size > 8 {
				return nil, errors.New("size must be a positive integer (<=8)")
			}
		case "-x":
			out.IsExpr = true
			// remaining args are going to be interpreted as expression
			out.Operand = strings.Join(args, " ")
			break loop
		default:
			if len(args) > 0 {
				return nil, fmt.Errorf("unknown option %q", args[0])
			}
			out.Operand = cmd
			break loop // only one arg left to be evaluated as a uint
		}

View on GitHub (pinned to a23773e6c3)

Solutions

1. Supply a value after -size, e.g. `x -size 8 <addr>`
2. Reorder flags so -size is not last, or remove it if the default size is fine
3. Check the client code that assembles the argument string for missing/empty substitutions

Example fix

// before
"x -count 4 -size 0xc000010000"
// after
"x -count 4 -size 8 0xc000010000"

if sizeArg == "" {
	return fmt.Errorf("-size requires a value")
}

When it happens

Trigger: Invoking `examineMemory` with `-size` as the trailing token, e.g. `x -count 4 -size 0x1000` or `x -size` with no operand at all.

Common situations: Truncated commands from IDE argument builders that drop trailing empty values; hand-typed commands where the size was forgotten; template strings where a substitution was empty.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• count/len must be a positive integer
• size must be a positive integer (<=8)
• no address specified
• too many arguments
• illegal commandline '%s'

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/587df53e4dc5b4db. Report an issue: GitHub.